The embodiments herein generally relate to acoustic wave generation and more particularly to coherent acoustic wave generation by electrically stimulated non-linear materials.
Unlike light amplification by stimulated emission of radiation (“LASER”) devices, acoustic waves traditionally are focused using high power, large system techniques. The ability to send and receive focused acoustic radiation over 100s to 1000s of meters currently requires large parabolic acoustic dishes that, at best, focus incoherent acoustic radiation into a solid angle about the direction of desired propagation. Alternatively, planar phased-arrays may be used to produce intense directional acoustic radiation.
Further, transmission of acoustic energy between two different media, e.g., a solid and a fluid, is difficult as there is a strong discontinuity of acoustic impedances at the interface between the two mediums. For example, acoustic waves typically propagate very fast in solids (e.g., steel) and much slower in fluids (e.g., air or water). If proper impedance matching is not provided, the energy does not transmit efficiently at the interface between the two mediums because energy is reflected at the interface back into the source of acoustic energy.